The present invention relates generally to the generation of test signal and more particularly to a signal generator and user interface for adding noise to selected portions of the test signal generated by the signal generator.
To check the operation of an electrical circuit under test, a test signal is provided to the circuit under test. A signal generator is an apparatus that provides such at test signal for checking the operation of the circuit under test. The signal generator has controls for setting-up the test signal according to user settings. The output signal from the electrical circuit may be observed by a measurement instrument, such as an oscilloscope or the like.
Various manufacturers provide user interfaces for setting-up test signals. One Example is the WinIQSIM™ Simulation Software, manufactured and sold by Rohde & Schwarz. The simulation software provides a user interface for setting-up digitally modulated signals and adding impairments to the signals. The user interface has a multi-carrier block diagram as shown in FIG. 1A having various blocks for defining parameters and setting impairments to the signal. Clicking on one of the blocks, such as the Data Source block, opens a data source dialog window as shown in FIG. 1B where the user can define data parameters or import a data file. Once the user has set the parameters of the data source, the user clicks the OK box and the dialog box closes. Clicking on the Modulation Setting block as shown in FIG. 2A opens a Modulation dialog window as shown in FIG. 2B where the user can set the modulation parameters of the signal. Clicking on the OK box closes the Modulation Setting dialog window. Clicking on the Noise block as shown in FIG. 3A and setting the Noise “On” opens a Noise dialog window as shown in FIG. 3B where the user can set noise levels for the signal. Clicking on the OK box closes the Noise dialog window.
A drawback to the above described user interface is that the noise impairment is applied to the total signal and is not to selected portions of the signal, such as the Preamble, Physical Layer Convergence Protocol (PLCP) Header, Payload or selected symbols within a WiMedia ultra wideband signal as defined by the WiMedia Alliance. Keeping selected portions of the WiMedia ultra wideband signal free of noise, such as the Preamble, allows the user to better discriminate the contribution of the added noise in the received signal, allowing the user to setup appropriate demodulation and channel equalization schemes.
What is needed is a user interface for use with a signal generator that allows a user to add noise to selected portions of test signal, such as pseudo random noise, additive white Gaussian noise (AWGN) and the like. The user should be able to select the location of the noise within the signal and set the level of noise to be produced.